System and method for compensating for motor magnetic disturbance of a compass measurement

Abstract

A method for correcting a vehicle compass measurement for an interfering magnetic field generated by a vehicle accessory, where the interfering magnetic field has an intensity sufficient to cause a compass measurement error, includes monitoring the operation of the vehicle accessory and detecting a characteristic of operation of the vehicle accessory. A measurement or timing signal is then generated based on the characteristic of operation. A magnetic field for direction is measured in response to the measurement signal and an offset or correction value is determined based at least one the measured magnetic field and the characteristic of operation of the vehicle accessory.

Description

FIELD OF THE INVENTION [0001] The present invention relates to magnetic direction sensing systems and particularly those for use in vehicles. BACKGROUND OF THE INVENTION [0002] The instrument panel (or cluster) of a vehicle is generally considered an unsuitable environment for an electronic compass. An electronic compass integrated into an instrument panel of a vehicle will detect a variety of magnetic disturbances that can affect the compass reading. Interfering magnetic fields are caused by various vehicle subsystems, such as, a motor for the vehicle HVAC system, an audio system, etc., and typically vary in magnitude. One significant source of interfering magnetic fields are stepper motors that are used to drive needles of gauges in the instrument panel for various vehicle functions such as speed, rpm, oil pressure, fuel level, and so on. Stepper motors for the instrument display gauges may be in close proximity to the magnetic sensors of the electrical compass integrated into an ...

AI Technical Summary

Benefits of technology

[0005] In another embodiment, a system for correcting a vehicle compass measurement for an interfering magnetic field generated by a vehicle accessory, where the interfering magnetic field has an intensity sufficient to cause a compass measurement error includes a magnetic field sensor for measuring a magnetic field for direction, a compass control circuit coupled to the magnetic field sensor, the compass control circuit configured to control the magnetic field sensor and to process the magnetic field measured by the magnetic field sensor, and an accessory control circuit coupled to the compass control circuit, the accessory control circuit configured to control the vehicle accessory and to provide a measurement signal to the compass control circuit instructing the compass control circuit to measure the magnetic field for direction based on a characteristic of operation of the vehicle accessory. In one embodiment, the correction value is determined by determining an average of a set of measured magnetic fields.

[0006] In yet another embodiment, a vehicle compass system for compensating for magnetic disturbances caused by a motor controlled by a motor control circuit includes a magnetic field sensor configured to sense the Earth's magnetic field and to generate orientation signals representative of the orientation of the magnetic field sensor with respect to the Earth's magnetic field and a control circuit configured to generate a heading based on a subset of orientation signals from the magnetic field sensor, the subset of orientation signals determined based on timin

Problems solved by technology

The instrument panel (or cluster) of a vehicle is generally considered an unsuitable environment for an electronic compass.

One significant source of interfering magnetic fields are stepper motors that are used to drive needles of gauges in the instrument panel for various vehicle functions such as speed, rpm, oil pressure, fuel level, and so on.

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